Ok, so you have a good start on an "entertainment" system. I would suggest the SBL platnium over the AE phillips. Other than that you have a great setup and should have no (as in zero) problems with conflicts.
Couple of thoughts, one, Don't use power DVD with the ATI radeon. It's a waste. The ATI card has HARDWARE decoding, last time I checked power DVD doesn't use it at all. Use either ATI's player or any other HARDWARE decoding player. As for adding a seperate preamp, it's totally frivalis(spelling). If you look around on the net you can find a few companies that have DTS,DSS,dolby prologic, and Dolby digital software, it works with the SB Plat, I don't remeber the site I found it on but you should be able to find it easily.
PS- I know what I am talking about, I run a business that builds custom computer and home entertainment systems. If you haven't already baught the parts e-mail me and I will send you some prices. Good luck in school.
PPS- I use only Klipsch Speakers. ALLWAYS and FOREVER
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Real life is just another window on my desktop!
-The Shadow